Server-side load balancing using parent-child link aggregation groups

ABSTRACT

Various exemplary embodiments relate to a method and related network node including one or more of the following: establishing, at the network node, a first Child Link Aggregation Group (CLAG), wherein the first CLAG includes at least one link to a first downstream node; establishing, at the network node, a second CLAG, wherein the second CLAG includes at least one link to a second downstream node; establishing, at the network node, a Parent Link Aggregation Group (PLAG), wherein the PLAG includes the first CLAG and the second CLAG; receiving, at the network node, a packet including an address of a destination of the packet; determining that the destination of the packet is associated with the PLAG; and transmitting the packet over both the first CLAG and the second CLAG.

TECHNICAL FIELD

Various exemplary embodiments disclosed herein relate generally to therouting of packets in a communications network and the balancing ofserver load.

BACKGROUND

In many client-server applications, such as IP Television (IPTV), thenumber of clients requesting a particular service can be quite large.Because any computer has finite processing capability, a server may onlyprovide service to a limited number of clients before the quality ofservice degrades to unacceptable levels. The most obvious solution,simply providing faster server components, can become prohibitivelyexpensive and technologically impossible as the number of active clientsincreases. Accordingly, many client-server applications provide multipleredundant servers in order to accommodate all client requests. Variousforms of load balancing are then employed to ensure that no singleserver becomes too bogged down in serving client requests.

In a rudimentary form of load balancing, multiple servers may beprovided and the client may simply choose one server to process arequest. This can be seen in applications such as file mirroring, wherea list of multiple computers serving the requested file are presented toa user, who then simply picks a server to download from. Otherinformation may be provided, such as the current status or geographiclocation of the server, but the onus is on the user to process thisinformation and make an informed server selection. If the chosen serverdoes not provide the quality of service expected by the client, adifferent server may be selected.

In another form of server load bat ancing, a client may send multiplerequests to multiple servers and simply accept the first response thatarrives, discarding any later arriving responses. Again, this requiresmore work on the part of the client, as the request must be duplicatedand transmitted to multiple addresses. A multicast protocol may be usedto send a single request to multiple destinations, but again, thismethod places the burden on the client, the servers and the network. Theserver(s) would need to know each client it serves and join a multicastgroup hosted by the client. This is not practical.

In a more advanced form of load balancing, a central server mayarbitrate from which server a client will receive service. According tothis method, a client may send its request to a central server whichwill then determine an appropriate working server to provide service tothe client. The central server may then either respond to the clientwith the address of the assigned working server or hand the initialrequest directly to the working server. Thus, this method can requirethe client to perform unnecessary session establishment and exposes theclient to at least a portion of the inner workings of the server system.This method may also carry the added disadvantage of leaving serversystem more vulnerable to attacks such as, for example, a denial ofservice attack.

Additionally, a central server would have the same limits as any othercomputing system and may likewise receive too many establishmentrequests to process efficiently. Thus, in particularly high clientvolume applications, multiple central servers may be required and theproblem becomes recursive. Another form of load balancing must then beimplemented in order to ensure that no central server receives morerequests than it can efficiently process.

Accordingly, there exists a need for a method of balancing server loadbetween multiple servers without needlessly complicating the methodsperformed by client devices in requesting a service. Additionally, aneed exists for a method to balance server load in a manner that isvirtually invisible to client devices.

Another possible point of failure for any network system is in the linksconnecting network nodes. IEEE 802.1AX, which is incorporated herein byreference, provides for link aggregation groups (LAGS) that combat thispossibility. A LAG is made up of multiple links between the same twonodes. When sending a packet over a LAG, a sending node simply selectsone of the links that make up the LAG and transmits the packet over oneof the selected link. A LAG is given an identifier such as the MACaddress of one of its constituent links. In this manner, a packet may betransmitted over one of multiple links toward its destination in amanner that is virtually invisible to all devices other than the twodevices at either end of the LAG. If one link fails, packets may stillbe transmitted over the remaining links in the LAG.

While effective in combating link failure and increasing transferspeeds, LAGs are not useful for many other problems. The operation of aLAG is very simple and not highly customizable. Thus, LAGs are notparticularly helpful when devising new and creative methods of fixingnetwork problems and increasing performance. Accordingly, there existsan additional need for a LAG implementation allowing a higher degree offunctionality and customization.

The foregoing objects and advantages of the invention are illustrativeof those that can be achieved by the various exemplary embodiments andare not intended to be exhaustive or limiting of the possible advantagesthat can be realized. Thus, these and other objects and advantages ofthe various exemplary embodiments will be apparent from the descriptionherein or can be learned from practicing the various exemplaryembodiments, both as embodied herein or as modified in view of anyvariation that may be apparent to those skilled in the art. Accordingly,the present invention resides in the novel methods, arrangements,combinations, and improvements herein shown and described in variousexemplary embodiments.

SUMMARY

In light of the present need for a method of balancing server loadbetween multiple redundant servers in a manner that is virtuallyinvisible to client devices, a brief summary of various exemplaryembodiments is presented. Some simplifications and omissions may be madein the following summary, which is intended to highlight and introducesome aspects of the various exemplary embodiments, but not to limit thescope of the invention. Detailed descriptions of a preferred exemplaryembodiment adequate to allow those of ordinary skill in the art to makeand use the inventive concepts will follow in later sections.

Various exemplary embodiments relate to a method and related networknode including one or more of the following: establishing, at thenetwork node, a first Child Link Aggregation Group (CLAG), wherein thefirst CLAG includes at least one link to a first downstream node;establishing, at the network node, a second CLAG, wherein the secondCLAG includes at least one link to a second downstream node;establishing, at the network node, a Parent Link Aggregation Group(PLAG), wherein the PLAG includes the first CLAG and the second CLAG;receiving, at the network node, a packet including an address of adestination of the packet; determining that the destination of thepacket is associated with the PLAG; and transmitting the packet overboth the first CLAG and the second CLAG.

It should be apparent that, in this manner, various exemplaryembodiments enable the routing of any packet to each of a group ofservers and the determination of which server should process and/orrespond to a received packet. In particular, by sending a packet overevery CLAG contained in a PLAG, each server connected to such a CLAGwill receive a copy of the packet. Thus, various exemplary embodimentsenable the transmission of a packet to multiple servers in a manner thatis virtually invisible to the client devices.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand various exemplary embodiments, referenceis made to the accompanying drawings, wherein:

FIG. 1 is a schematic diagram of an exemplary network for routing aunicast or multicast packet to multiple servers;

FIG. 2 is a schematic diagram of an exemplary routing node for routing aunicast or multicast packet to multiple servers;

FIG. 3 is a schematic diagram of an exemplary data arrangement forstoring data related to IP address resolution;

FIG. 4 is a schematic diagram of an exemplary data arrangement forstoring Child Link Aggregation Group configurations;

FIG. 5 is a schematic diagram of an exemplary data arrangement forstoring Parent Link Aggregation Group configurations;

FIG. 6 is a schematic diagram of an exemplary network for performingload balancing between multiple servers;

FIG. 7 is a schematic diagram of an exemplary data arrangement forstoring an indexed list of currently active servers;

FIG. 8 is a flowchart of an exemplary method for routing a unicast ormulticast packet to multiple servers; and

FIG. 9 is a flowchart of an exemplary method for performing loadbalancing between multiple servers.

DETAILED DESCRIPTION

Referring now to the drawings, in which like numerals refer to likecomponents or steps, there are disclosed broad aspects of variousexemplary embodiments. It should be noted that, while various examplesutilize letters to signify various network addresses, these lettersserve as placeholders and, in actual operation, valid network addressesformed according to appropriate standards would likely be present. Inaddition, while various embodiments are described herein as routing IPpackets specifically, the present disclosure is in no way limited tothis protocol.

FIG. 1 is a schematic diagram of an exemplary network 100 for routing aunicast or multicast packet to multiple servers. Exemplary network 100may include a sending node 110, a communications network 120, a routingnode 130, and a number of receiving nodes 140 a, 140 b, 140 c.

Sending node 110 may be a device that communicates with receiving nodes140 a, 140 b, 140 c. Sending node 110 may, for example, act as a clientdevice and provide a user with access to a service that may be providedby receiving nodes 140 a, 140 b, 140 c. More specifically, in variousexemplary embodiments, sending node 110 is a personal or laptopcomputer, wireless email device, cell phone, television set-top box, orany other device capable of sending a packet to another network device.Sending node 110 may be associated with an IP address, such as “D.”Sending node 110 may also be associated with a MAC address.

Communications network 120 may be any network for providing datacommunications between sending node 110 and router node 130.Communications network 120 may be packet-switched or circuit-switched.Further, communications network 120 may provide, for example, phone andInternet service to various user devices in communication withcommunications network 120.

Routing node 130 may be a device that receives and retransmits packetsaccording to their destination address. More specifically, in variousexemplary embodiments, routing node 130 is a packet router, networkswitch, multilayer switch, server, or any other device capable ofreading an address and forwarding a packet over a port associated withthe address. Routing node 130 may be associated with at least one MACaddress, “T.” while it is likely that routing node 130 is associatedwith multiple MAC addresses, for simplicity, T will be used herein torefer to any appropriate MAC address of the MAC addresses associatedwith routing node 130.

Receiving nodes A-C 140 a, 140 b, 140 c may be network devices thatcommunicate with sending node 110. Receiving nodes A-C 140 a, 140 b, 140c may be server devices that provide a service to user node 110 such as,for example, IP television or file access. More specifically, in variousexemplary embodiments, each of receiving nodes A-C 140 a, 140 b, 140 cmay be a server, a personal or laptop computer, wireless email device,cell phone, television set-top box, or any other device capable ofreceiving a packet from another network device.

Receiving node A 140 a may be associated with an IP address A and anumber of MAC addresses, such as U and V. Receiving node B, 140 b may beassociated with an IP address B and a number of MAC addresses, such asW, X, and Y. Receiving node C, 140 c may be associated with an IPaddress C and a number of MAC addresses, such as Z. It should beapparent that each of receiving nodes A-C 140 a, 140 b, 140 c, may haveany number of network interfaces and thus any number of MAC addresses,including a single MAC address, as is the case with exemplary receivingnode C 140 c. Receiving nodes A-C 140 a, 140 b, 140 c may includeadditional network interfaces that are not coupled to routing node 130,but for the purposes of the examples described herein, MAC addresses U,V, W, X, Y, and Z are each associated with network interfaces connectedto routing node 130.

Having described the components of network 100, a brief summary of theoperation of network 100 will be provided. It should be apparent thatthe following description is intended to provide an overview of theoperation of network 100 and is therefore a simplification in somerespects. The detailed operation of network 100 will be described infurther detail below in connection with FIGS. 2-5 and 8.

According to various exemplary embodiments, sending node may transmit apacket over communications network 120. The packet may be addressed toIP address A (i.e., the IP address associated with receiving node A 140a) and may be carried inside a frame 150 a to the next device withincommunications network 120. Routing node 130 may then receive the packetinside a frame 150 b addressed to MAC address T. In determining overwhich port the packet should be forwarded, routing node 130 may read theIP address of the packet and consult its configuration to determine howto process the packet. In this example, routing node 130 may determinethat it has been configured to transmit packets addressed to IP addressA to all three of the receiving nodes 140 a, 140 b, 140 c. Routing node130 may then select a link over which to transmit the packet toreceiving node A 140 a, a link over which to transmit the packet toreceiving node B 140 b, and a link over which to transmit the packet toreceiving node C 140 c. Finally, routing node 130 may transmit a frame150 c to the interface with MAC address U, a frame 150 d to theinterface with MAC address Y, and a frame 150 e to the interface withMAC address Z.

Thus, the packet sent by sending node 110 to IP address A has beenreceived at each receiving node 140 a, 140 b, 140 c without specialaction on the part of sending node 110. Receiving nodes 140 a, 140 b,140 c are now free to determine which, if any, of the receiving nodes140 a, 140 b, 140 c should respond to the packet. An exemplary methodfor determining which node should respond to such a packet is describedherein with reference to FIGS. 6-7 and 9. The process may be similar forvarious embodiments that are not specifically tied to IP. In theseembodiments, the payload of the frame received by routing node 130,whatever it is, may be transmitted to each of the receiving nodes 140 a,140 b, 140 c.

FIG. 2 is a schematic diagram of an exemplary routing node 200 forrouting a unicast or multicast packet to multiple servers. Exemplaryrouting node 200 may correspond to routing node 130 and may include afirst interface 210, an address resolution module 220, an addressresolution storage 230, a link aggregation module 240, a linkaggregation control storage 250, and a plurality of interfaces 260 u-z.

Interface 210 may be an interface comprising hardware and/or executableinstructions encoded on a machine-readable storage medium configured totransmit and receive data over communications network 120. Interface 210may be coupled to another network device within communications network120.

Address resolution module 220 may include hardware and/or executableinstructions on a machine-readable storage medium configured todetermine how to route a packet according to its destination address.For example, address resolution module 220 may receive a packet frominterface 210 and read its destination address. Address resolutionmodule 220 may then consult address resolution storage 230 to determinea next-hop address associated with the destination address. Addressresolution module 220 may finally pass the packet to link aggregationmodule 240 so it may forward the packet according to the determinednext-hop address.

Address resolution storage 230 may be any machine-readable mediumcapable of storing associations between destination addresses andidentifiers used to route a packet. For example, address resolutionstorage 230 may be a table implemented according to the AddressResolution Protocol and thus provide associations between IP addressesand MAC addresses. An exemplary embodiment of the data stored in addressresolution storage 230 is described in greater detail below withreference to FIG. 3.

Link aggregation module 240 may include hardware and/or executableinstructions on a machine-readable storage medium configured to transmita packet over an appropriate interface 260 u-z. Link aggregation module240 may implement at least one Parent Link Aggregation Group (PLAG) andconstituent Child Link Aggregation Groups (CLAGs).

A CLAG may be configured to include one or more links to another networknode. Each CLAG may be associated with a CLAG identifier. This CLAGidentifier may be a unique identifier or it may be an identifierassociated with one of the included links, such as its MAC address. Inoperation, when forwarding a packet over a CLAG, the link aggregationmodule 240 may select one of the links included in the CLAG and transmitthe packet over only the selected link. In this manner, link redundancyis established and if one link in the CLAG fails, the remaining linksmay be used to communicate with the attached network node.

A PLAG may be configured to include multiple CLAGs. Each CLAG mayconnect to a different network node or the same network node. A PLAG maybe associated with a PLAG identifier which may be a unique identifier orthe same as the CLAG identifier for one of the included CLAGs. Inoperation, when forwarding a packet over a PLAG, the link aggregationmodule 240 may forward the packet over each constituent CLAG. The packetmay then be forwarded according to the normal operation of theconstituent CLAGs, as described above. Thus, a packet forwarded over aPLAG will be sent over one link from each constituent CLAG. When eachCLAG connects to a different network node, each network node willreceive one copy of the packet and can then process it accordingly.

According to the exemplary embodiment in FIG. 2, routing node 200 isconfigured with one PLAG and three CLAGs. A first CLAG has SAC address Uas an identifier and includes interfaces 260 u, 260 v. A second CLAG hasMAC address W as an identifier and includes interfaces 260 w, 260 x, 260y. A third CLAG has MAC address Z as an identifier and includesinterface 260 z. The PLAG has MAC address U as an identifier andincludes CLAG U, CLAG W, and CLAG Z.

Link aggregation control storage 250 may be any machine-readable mediumcapable of storing the configuration of various link aggregationsgroups. Link aggregation control storage 250 may, for example, containthe definitions of all PLAGs and CLAGs configured on routing node 200.Exemplary embodiments of the data stored by link aggregation controlstorage 250 are described in further detail below with reference toFIGS. 4-5.

Interfaces 260 u-z may each be an interface comprising hardware and/orexecutable instructions encoded on a machine-readable storage mediumconfigured to transmit and receive data. Each interface 260 u-z may becoupled to one of a plurality of network nodes. For example, interfaces260 u, 260 v may be coupled to receiving node A 140 a; interfaces 260 w,260 x, 260 y may be coupled to receiving node B 140 b; and interface 260z may be coupled to receiving node C 140 c.

FIG. 3 is a schematic diagram of an exemplary data arrangement 300 forstoring data related to IP address resolution. Data arrangement 300 maybe, for example, a table in a database stored in address resolutionstorage 230. Alternatively, data arrangement 300 could be a series oflinked lists, an array, or a similar data structure. Thus, it should beapparent that data arrangement 300 is an abstraction of the underlyingdata; any data structure suitable for storage of this data may be used.

Data arrangement 300 may include IP address field 310, corresponding MACaddress field 320, and time to live (TTL) field 330. IP address field310 may be used to indicate the IP address to which a particular recordcorresponds. MAC address field 320 may indicate a MAC address whichshould be used to route packets to the corresponding IP address. TTLfield 330 may indicate when a particular record should be deleted fromdata arrangement 300.

As an example, record 340 indicates that packets destined for IP addressA should be forwarded over the interface associated with MAC address Uand that this mapping should live until 21:12:00, at which point record340 may be deleted. Likewise, record 350 indicates that IP address Balso maps to MAC address U and that the mapping should live until09:01:25. Record 360 indicates that IP address C maps to MAC address Uas well and that this mapping should live until 00:51:50. Dataarrangement 300 may contain numerous additional records 370.

FIG. 4 is a schematic diagram of an exemplary data arrangement 400 forstoring CLAG configurations. Data arrangement 400 may be, for example, atable in a database stored in link aggregation control storage 250.Alternatively, data arrangement 400 could be a series of linked lists,an array, or a similar data structure. Thus, it should be apparent thatdata arrangement 400 is an abstraction of the underlying data; any datastructure suitable for storage of this data may be used.

Data arrangement 400 may include CLAG address field 410 and linkaddresses field 420. CLAG address field 410 may indicate the CLAGidentifier to which a CLAG record corresponds. Link addresses field 420may indicate the MAC addresses that are associated with a particularCLAG address.

As an example, CLAG record 430 indicates that a CLAG is configured thathas MAC address U as an identifier and includes the interfacesassociated with MAC addresses U and V. Likewise, CLAG record 440indicates that a CLAG is configured that has MAC address W as anidentifier and includes the interfaces associated with MAC addresses W,X, and Y. Further, CLAG record 450 indicates that a CLAG is configuredthat has MAC address Z as an identifier and includes the interfaceassociated with MC address Z. Data arrangement 400 may contain numerousadditional CLAG records 460.

FIG. 5 is a schematic diagram of an exemplary data arrangement 500 forstoring PLAG configurations. Data arrangement 500 may be, for example, atable in a database stored in link aggregation control storage 250.Alternatively, data arrangement 500 could be a series of linked lists,an array, or a similar data structure. Thus, it should be apparent thatdata arrangement 500 is an abstraction of the underlying data; any datastructure suitable for storage of this data may be used.

Data arrangement 500 may include PLAG address field 510 and CLAGaddresses field 520. PLAG address field 510 may indicate the PLAGidentifier to which a PLAG record corresponds. CLAG addresses field 520may indicate the CLAG identifiers that are associated with a particularPLAG address.

As an example, PLAG record 530 indicates that a PLAG is configured thathas MAC address U as an identifier and includes the CLAGs identified byMAC addresses U, W, and Z. Data arrangement 500 may contain numerousadditional PLAG records 540.

FIG. 6 is a schematic diagram of an exemplary network 600 for performingload balancing between multiple servers 140 a, 140 b, 140 c. Exemplarynetwork 600 may include routing node 130, receiving nodes A-C 140A,140B, 140C, and control node 610.

Control node 610 may be a network device capable of keeping receivingnodes 140 a, 140 b, 140 c up-to-date as to which receiving nodes 140 a,140 b, 140 c are active. More specifically, in various exemplaryembodiments, control node 610 may be a server, a personal or laptopcomputer, wireless email device, cell phone, television set top box, orany other device capable of communicating with each receiving node 140a, 140 b, 140 c. Control node 610 may maintain a list of activereceiving nodes 140 a, 140 b, 140 c and periodically communicate thislist to receiving nodes 140 a, 140 b, 140 c. Alternatively, control node610 may only send messages to receiving nodes 140 a, 140 b, 140 c when areceiving node 140 a, 140 b, 140 c becomes active or inactive andreceiving nodes 140 a, 140 b, 140 c may then update locally-storedactive server lists accordingly. As a further alternative, control node610 may not be present at all and receiving nodes 140 a, 140 b, 140 cmay maintain local active server lists through periodic communicationswith each other.

Receiving nodes 140 a, 140 b, 140 c may all implement an algorithm thatuses a list of the currently active receiving nodes 140 a, 140 b, 140 cto determine whether or not to process a received packet and respondaccordingly. Thus, assuming each receiving node 140 a, 140 b, 140 ccontains a reference to all three receiving nodes 140 a, 140 b, 140 c intheir currently active server list, when receiving node A 140 a receivesframe 150 c, it may use the common algorithm to determine that receivingnode C 140 c should respond to the packet. Accordingly, receiving node A140 a may ignore the packet. Likewise, when receiving node B 140 breceives frame 150 d, it may determine that receiving node C 140 cshould respond to the packet and ignore the packet as well. Whenreceiving node C 140 c receives frame 150 e, it may determine that,according to the algorithm, it should process the packet and respondaccordingly. Receiving node C 140 c may therefore send a response packetaddressed to IP address D (i.e., the IP address of sending node 110) andencapsulate it in a frame 620 addressed to MAC address T.

FIG. 7 is a schematic diagram of an exemplary data arrangement 700 forstoring an indexed list of currently active servers. Data arrangement700 may be, for example, a table in a database stored in one of thereceiving nodes 140 a, 140 b, 140 c. Alternatively, data arrangement 700could be a series of linked lists, an array, or a similar datastructure. Thus, it should be apparent that data arrangement 700 is anabstraction of the underlying data; any data structure suitable forstorage of this data may be used.

Data arrangement 700 may include an index field 710 and a server IDfield 720. Index field 710 may simply include a number corresponding toa specific record. Records may be accessed by specifying the index ofthe desired record. Server ID field 720 may include an identifier forone of the receiving nodes 140 a, 140 b, 140 c. The identifier may be,for example, an IP address associated with the referenced receiving node140 a, 140 b, 140 c.

As an example, server record 730 may be indexed by the number zero andidentify the node at IP address A (i.e., receiving node A 140 a) as anactive server. Likewise, server record 740 may be indexed by the numberone and identify the node at IP address B (i.e., receiving node B 140 b)as an active server. Server record 750 may be indexed by the number twoand identify the node at IP address C (i.e., receiving node C 140 c) asan active server. Data arrangement 700 may contain numerous additionalrecords 760.

FIG. 8 is a flowchart of an exemplary method 800 for routing a unicastor multicast packet to multiple servers. Method 800 may be performed bythe components of routing node 130 to forward a packet to each of thereceiving nodes 140 a, 140 b, 140 c.

Method 800 starts in step 805 and proceeds to step 810, where routingnode 130 receives a packet. Routing node 130 may then determine thedestination IP address of the packet and resolve the destination IPaddress into an appropriate MAC address over which to forward the packetin steps 815 and 820, respectively. For example, routing node 130 mayconsult an address resolution storage 230 to determine a MAC addressassociated with the destination IP address. After determining anappropriate MAC address for forwarding the packet, routing node 130 maydetermine whether the MAC address is associated with a PLAG in step 825.

If the MAC address identifies a PLAG, method 800 may proceed to step830, where routing node 130 may retrieve a list of CLAGs associated withthe PLAG by, for example, accessing a PLAG record associated with thePLAG address in a link aggregation control storage 250. Routing node 130may then retrieve a list of links associated with the first CLAG in thelist of CLAGs at step 835 by, for example, accessing a CLAG recordassociated with the first constituent CLAG from a link aggregationcontrol storage 250. Routing node 130 may then select one link from thelist of links for the CLAG and transmit the packet to the selected linkin steps 840 and 845, respectively. Method 800 may then proceed to step850, where routing node 140 may determine whether it has reached the endof the list of CLAG addresses. If it has not, method 800 may return tostep 835 where routing node 140 may repeat steps 835-850 for the nextCLAG in the list. If the end of the list has been reached, method 800may stop in step 880. In this manner, one copy of the received packetmay be sent over each CLAG.

If it is determined at step 825 that the MAC address does not identify aPLAG, method 800 may move to step 855, where routing node 130 maydetermine whether the MAC address is instead associated with a CLAG. Ifso, routing node 130 may retrieve a list of links associated with theCLAG, select one link from the list, and transmit the packet to theselected link in steps 860, 865, and 870, respectively. Method 800 maythen stop in step 880. In this manner, the routing node 130 mayimplement standard link aggregation functionality in addition to PLAGfunctionality.

If routing node 130 determines at step 855 that the MAC address is notassociated with a CLAG, routing node 130 may assume that the packet maybe routed according to standard operation. Method 800 may proceed tostep 875 where routing node 130 may transmit the packet to the MACaddress associated with the destination IP address and then stop in step880.

FIG. 9 is a flowchart of an exemplary method 900 for performing loadbalancing between multiple servers. Method 900 may be performedindependently by the components of each of the receiving nodes 140 a,140 b, 140 c, to determine whether to process a received packet andrespond accordingly.

Method 900 may start in step 905 and proceed to step 910, where thereceiving node 140 a, 140 b, 140 c may receive a packet that has beensent to all receiving nodes 140 a, 140 b, 140 c. The receiving node 140a, 140 b, 140 c may then extract a number of fields and otherinformation from the packet at step 915. The extracted information mayinclude, for example, the source IP address or the type of servicerequest. Method 900 may then proceed to step 920, where the receivingnode 140 a, 140 b, 140 c may calculate a hash value from the extractedfields using any method known to those of skill in the art. In step 925,receiving node 140 a, 140 b, 140 c may then determine how many totalreceiving nodes 140 a, 140 b, 140 c are currently active by, forexample, consulting a locally-stored active server list.

Receiving node 140 a, 14Gb, 140 c may then calculate an index valueusing the hash value and the total number of servers at step 930. Forexample, receiving node 140 a, 140 b, 140 c may perform a modulooperation on the hash function using the total number of active servers.It should be apparent that in this manner, an index value is obtainedhaving a value between zero and the total number of active servers minus1, inclusive. Receiving node 140 a, 140 b, 140 c may then, in step 935,access an item in the list of active servers associated with thecalculated index.

In step 940, receiving node 140 a, 140 b, 140 c will determine whetherthe accessed item identifies itself or another receiving node 140 a, 140b, 140 c. If the receiving node 140 a, 140 b, 140 c determines that theaccessed item identifies itself, method 900 may proceed to step 945where the receiving node 140 a, 140 b, 140 c may process the receivedpacket and respond accordingly. For example, if the received packet wasa request for a change of channel in an IPTV system, the receiving node140 a, 140 b, 140 c may respond by transmitting a new channel to sendingnode 110. Method 900 may then stop at step 955. If, on the other hand,receiving node 140 a, 140 b, 140 c determines in step 940 that theaccessed item identifies a different receiving node 140 a, 140 b, 140 c,it may simply ignore the packet in step 950 and method 900 may then stopin step 955. In should be apparent that, in the manner described above,only one of the receiving nodes 140 a, 140 b, 140 c will process andrespond to each received packet.

Having described exemplary components and methods for the operation ofexemplary networks 100, 600, an example of the operation of exemplarynetworks 100, 600 will now be provided with reference to FIGS. 1-9.

The address resolution storage 230 of routing node 130 may be indicatedby data arrangement 300. The link aggregation control storage 250 ofrouting node 130 may be indicated by data arrangements 400, 500. Controlnode 610 may currently be monitoring the status of receiving nodes 140a, 140 b, 140 c and transmit a list indicating all receiving nodes 140a, 140 b, 140 c as currently active to each of the receiving nodes 140a, 140 b, 140 c. Accordingly, each receiving node 140 a, 140 b, 140 cmay currently contain a list of active servers as indicated by dataarrangement 700.

The process may begin with sending node 110 transmitting a packet withdestination IP address A over communications network 120 inside frame150 a. Routing node 130 may receive the packet inside frame 150 b.Address resolution module 220 of routing node 130 may then determinethat the destination IP address of the packet is A. By accessing record340 in address resolution storage, address resolution module 220 maydetermine that IP address A is associated with MAC address U. The packetmay then be passed to link aggregation module 240 which may determinethat MAC address U is associated with a PLAG. By accessing PLAG record530 contained in link aggregation control storage 250, link aggregationmodule 240 may determine that PLAG U contains CLAG U, CLAG W, and CLAGZ.

Link aggregation module 240 may then access CLAG record 430 anddetermine that interface addresses U and V are contained by CLAG U. Linkaggregation module 240 may then select interface address U and transmitthe packet in frame 150 c to receiving node A 140 a via interface 260 u.Moving on to CLAG W, link aggregation module may access CLAG record 440and select interface address Y from the resulting list of threeinterface addresses associated with CLAG W. Link aggregation module 240may then transmit the packet in frame 150 d to receiving node B 140 bvia interface 260 y. Finally, link aggregation module may access record450, select interface address Z from the list of interface addressesassociated with CLAG Z, and transmit the packet in frame 150 e toreceiving node C 140 c via interface 260 z.

After receiving the packet, each receiving node 140 a, 140 b, 140 c maydetermine whether to respond to the packet by first extracting thesource IP address and the request type from the packet. For example, thesource IP address may be D and the type of request may be a request fora specific file. Using this information, each receiving node 140 a, 140b, 140 c may calculate a hash value from the extracted values, such as,for example, “0x4F31.” Each receiving node 140 a, 140 b, 140 c may thendetermine how many servers are currently active by, for example,counting the number of records in data arrangement 700. In this example,the total number of active servers is three. Each receiving server maythen obtain a calculated index of two by performing a modulo operationon the hash value using the total number of active servers, three.

Each receiving node may then retrieve server record 750, i.e. the serverrecord having an index of two. Receiving node A and B 140 a, 140 b mayboth determine that this server record does not identify themselves andthus may simply discard the packet. Receiving node C 140 c, on the otherhand, may recognize this server record as identifying itself and createa response packet addressed to IP address D. Receiving node C 140 c maythen transmit the response packet to sending node 100 within frame 220.

According to the foregoing, various exemplary embodiments provide forbalancing server load between multiple servers in a manner that isvirtually invisible to clients. In particular, by implementing a ParentLink Aggregation Group including multiple Child Link Aggregation Groups,any packet can be forwarded at Layer 2 to multiple servers at the end ofeach CLAG. Further, by implementing a selection algorithm across all ofthe servers, the servers can quickly and efficiently determine oneserver that should process the packet.

It should be apparent from the foregoing description that variousexemplary embodiments of the invention may be implemented in hardwareand/or firmware. Furthermore, various exemplary embodiments may beimplemented as instructions stored on a machine-readable storage medium,which may be read and executed by at least one processor to perform theoperations described in detail herein. A machine-readable storage mediummay include any mechanism for storing information in a form readable bya machine, such as a network node (e.g. router or switch). Thus, amachine-readable storage medium may include read-only memory (ROM),random-access memory (RAM), magnetic disk storage media, optical storagemedia, flash-memory devices, and similar storage media.

Although the various exemplary embodiments have been described in detailwith particular reference to certain exemplary aspects thereof, itshould be understood that the invention is capable of other embodimentsand its details are capable of modifications in various obviousrespects. As is readily apparent to those skilled in the art, variationsand modifications can be affected while remaining within the spirit andscope of the invention. Accordingly, the foregoing disclosure,description, and figures are for illustrative purposes only and do notin any way limit the invention, which is defined only by the claims.

1. A method of routing packets in a communications network by a networknode, the method comprising: establishing, at the network node, a firstChild Link Aggregation Group (CLAG), wherein the first CLAG includes atleast one link to a first downstream node; establishing, at the networknode, a second CLAG, wherein the second CLAG includes at least one linkto a second downstream node; establishing, at the network node, a ParentLink Aggregation Group (PLAG), wherein the PLAG includes the first CLAGand the second CLAG; receiving, at the network node, a packet includingan address of a destination of the packet; determining that thedestination of the packet is associated with the PLAG; and transmittingthe packet over both the first CLAG and the second CLAG.
 2. The methodof claim 1, wherein the packet is a unicast packet.
 3. The method ofclaim 1, further comprising: associating a Layer 2 address with thePLAG; associating an address of the first downstream node with the Layer2 address; and associating an address of the second downstream node withthe Layer 2 address, wherein the step of determining that thedestination of the packet is associated with the PLAG comprisesdetermining that the address of the destination of the packet isassociated with the Layer 2 address.
 4. The method of claim 3, wherein:the steps of associating an address of the first downstream node andassociating an address of the second downstream node with the Layer 2address both comprise modifying an Address Resolution Protocol (ARP)table; and the step of determining that the address of the destinationof the packet is associated with the Layer 2 address comprises readingan entry of the ARP table, the entry being associated with the addressof the destination of the packet.
 5. The method of claim 1, wherein thestep of transmitting the packet over both the first CLAG and the secondCLAG comprises: selecting a first chosen link of the at least one linkincluded in the first CLAG; selecting a second chosen link of the atleast one link included in the second CLAG; constructing a first framethat includes the packet and an address associated with the first chosenlink; constructing a second frame that includes the packet and anaddress associated with the second chosen link; forwarding the firstframe to the first downstream node over the first chosen link; andforwarding the second frame to the second downstream node over thesecond chosen link.
 6. The method of claim 1, further comprising: at thefirst downstream node: receiving a list of all downstream nodes thatreceive frames via the PLAG, determining a total number of downstreamnodes from the list, receiving the first frame from the network node,deriving a piece of information from the first frame, performing amathematical operation on the piece of information using the totalnumber of downstream nodes to obtain a result index, determining whetherthe result index corresponds to the first downstream node, responding tothe first frame when the result index corresponds to the firstdownstream node, and discarding the first frame when the result indexdoes not correspond to the first downstream node.
 7. The method of claim6, further comprising: at the first downstream node, arranging the listof all downstream nodes in an array in increasing order of a nodeidentifier associated with each downstream node, wherein the step ofdetermining whether the result index corresponds to the first downstreamnode comprises: reading an element from the array, wherein an index ofthe element is equal to the result index, and determining whether theelement includes an identification of the first downstream node.
 8. Themethod of claim 6, wherein the mathematical operation is a modulooperation.
 9. The method of claim 6, wherein the step of deriving apiece of information from the frame comprises calculating a hash valuefrom at least one field of the frame.
 10. The method of claim 9, whereinthe at least one field of the frame includes a source IP address. 11.The method of claim 1, wherein the first downstream node and the seconddownstream node are both Internet Protocol Television (IPTV) videoservers.
 12. A network node for routing packets in a communicationsnetwork, the network node connected to a first downstream node and asecond downstream node, the network node comprising: an interface thatreceives a packet, the packet including a destination address; aplurality of interfaces, including at least one interface connected tothe first downstream node and at least one interface connected to thesecond downstream node; a link aggregation control storage that stores:a first Child Link Aggregation Group (CLAG) record that includes a firstCLAG identifier and an indication of the at least one interface of theplurality of interfaces that is connected to the first downstream node,a second CLAG record that includes a second CLAG identifier and anindication of the at least one interface of the plurality of interfacesthat is connected to the second downstream node, and a Parent LinkAggregation Group (PLAG) record that includes a PLAG identifier, thefirst CLAG identifier, and the second CLAG identifier; an addressresolution module that determines that the destination address of thepacket is associated with the PLAG identifier; and a link aggregationmodule that: determines that the PLAG identifier is associated with thefirst CLAG identifier and the second CLAG identifier by retrieving thePLAG record from the link aggregation control storage, selects a firstselected interface from the at least one indication of an interface ofthe first CLAG record, selects a second selected interface from the atleast one indication of an interface of the second CLAG record, forwardsthe packet over the first selected interface and the second selectedinterface.
 13. The network node of claim 12, further comprising: anaddress resolution storage that stores: a first address resolutionrecord identified by an address of the first downstream node andincluding the PLAG identifier, and a second address resolution recordidentified by an address of the second downstream node and including thePLAG identifier; and in determining that the destination address of thepacket is associated with the PLAG identifier, the address resolutionmodule retrieves an address resolution record identified by thedestination address of the packet.
 14. The network node of claim 12,wherein the packet is a unicast packet.
 15. The network node of claim12, wherein the first downstream node and the second downstream node areboth Internet Protocol Television (IPTV) video servers.
 16. Amachine-readable storage medium that contains instructions for routingpackets by a network node in a communications network, themachine-readable storage medium comprising: instructions for receiving,from a Layer 2 (L2) client, an input frame having an input L2 address asa destination address; instructions for determining that the input L2address is associated with a Parent Link Aggregation Group (PLAG);instructions for determining a first Child Link Aggregation Group (CLAG)and a second CLAG associated with the PLAG; instructions for determininga first L2 interface associated with the first CLAG and a second L2interface associated with the second CLAG; instructions for extracting apayload rom the input frame; instructions for creating a first outgoingframe and a second outgoing frame, both including the payload extractedfrom the intermediate frame; instructions for passing the first outgoingframe to the first L2 interface; and instructions for passing the secondoutgoing frame to the second L2 interface.
 17. The machine-readablereadable storage medium of claim 16, further comprising: instructionsfor determining a first outgoing L2 address associated with the first L2interface; and instructions for determining a second outgoing L2 addressassociated with the second L2 interface, wherein the first outgoingframe includes the first outgoing L2 address as a destination addressand the second outgoing frame includes the second outgoing L2 address asa destination address.
 18. The machine-readable readable storage mediumof claim 17, wherein the first outgoing L2 address is the same as theinput L2 address.
 19. The machine-readable readable storage medium ofclaim 16, wherein the first L2 interface is one L2 interface of aplurality of L2 interfaces associated with the first CLAG.
 20. Themachine-readable storage medium of claim 16, wherein the input L2address is a MAC address and the L2 client is a client of the MACsublayer.